In general, a bore of a cylinder block may be temporarily or permanently distorted by the fastening torque of a cylinder head bolt, coolant temperature, and a combustion pressure of a combustion chamber, etc. When such distortion of a cylinder is excessive, the engine may consume excessive lubricant.
Therefore, bore distortion should be precisely measured with respect to various engine operating conditions to assist in engine design.
According to an apparatus for measuring a bore distortion of a cylinder block of the prior art, bore distortion caused by a fastening torque of a cylinder head bolt was the only factor that could be precisely measured. Measurement of bore distortion of a cylinder caused by variations in coolant temperature showed a large error or the apparatus for measuring such bore distortion was very inefficient or uneconomical.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should  not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.